correct belt length

[davidwf]

On my ancient but fully working LTH130 I replaced the cutter deck belt with, what appeared to be the correct part but the blades rotate (against the brakes!) as soon as the engine starts ...... putting the old belt back it doesnt happen so clearly the belt is too short..... this is the one I bought https://www.mowerpartsales.com/husq...-lt100-lt112-lt120-lt125--532131264-131-p.asp
The belt supplied is 78" so I am wondering whether a 79" one is correct....does anyone KNOW FOR SURE please....I do recall having this problem around 5 years ago when I last replaced it but didnt save the details

thanks
attached pics of the id plate and the belt purchased

 

[OldDiyer]

Before you start spending more money on a longer belt take the time to measure your old belt than check the new belt and see if it is correct or not. Many postings on this site about belts new from different company's that are not correct even thu they are marked with correct length. If you are not sure on how to do the measurements just google it and watch it from one of the belt manufacturers.

 

[davidwf]

thanks but... it is extremely difficult to accurately measure the belts....holding them up side by side they "look" about the same....but clearly they are not, hence my request
....and just to add another spanner in the works it looks like I have a 38" deck...i.e. 2 x 19" blades!

 

[ILENGINE]

Looks like the OEM belt is 1/2 x 78-1/2 so your belt is too short. And that is the reason we insist on people using OEM belts instead of trying to be cheap and then cause bigger issues. The OEM belt suggested list is like $25 us

 

[davidwf]

Thanks...wow...by a whole 1/2"....?

 

[ILENGINE]

Thanks...wow...by a whole 1/2"....?

I hear the sarcasm but since a lot of OEM belts are not standard width or cut angle that 1/2 inch can be a mile. What people don't realize is just because the belt equivalent chart shows a belt as 1/2 inch width doesn't mean the OEM belt is 1/2 inch. MTD as an example most belt equivalent charts show their belts at 5/8 width but in reality they are 21/32. JD is bad about using proprietory belt cut angles which are not reflected in most belt charts

 

[davidwf]

thank you.... may I ask where you got this info from... maybe post a link so that I can go back to the supplier with evidence
thanks

 

[ILENGINE]

thank you.... may I ask where you got this info from... maybe post a link so that I can go back to the supplier with evidence
thanks

Here is a couple examples https://rotarycorp.com/search?q=532131264 https://www.amazon.com/Husqvarna-532131264-V-Belt/dp/B0028BL7RE

 

[davidwf]

Thank you....I wonder why, here in the UK they are shown as 78"

 

[bertsmobile1]

hold both of your belts side by side in one hand
Draw a line across both of them ( I use a white paint pen )
Now while holding them tightly together with one had pull then through the other say 1 foot
Without letting the belts loose move your hands together then pull another foot through.
Continue shuffleing the belts through your hands till you get back to the line you drew
It should be a straitish line across both belts if they are the same length .
I allow about 1/4" of difference ( old slightly longer ) .
In theory V belts do not stretch, they get thinner so sit deeper in the grooves that become loose and people assume they have stretched .
It takes a little bit of practice because the old belt will be loose & very flexiable while the new belt will be quite stiff with some hard bends where it was folded for storeage .
My go to for belt dimensions is always the Gates Catalogue as it shows the real length, the outside length & the effective length plus the actual belt width & angle plus depth .
Gates do make exact OEM spec belts in their Lawn & garden range in this case it is a 6458BR and of course the size look up is currently not working ( Murphy strikes again)
Now UK ( & OZ ) measure belts by their inner length & the USA measure them by their out side length and on a 1/2 " belt that is ≈ 2" longer than the inside length
Getting my head around belts was by far the hardest part of becoming a mower tech .